Rice

Rice is the principal food crop in practically all the tropical realons
of the world as well as in most subtropical areas and in some temperate zone
areas having a relatively long growing season. Probably half of the world
population depends on rice for its major food source. Rice is grown on around
200 million acres outside of Communist China - where data are not available.
Probably an additional 100 million acres are grown there. World production
outside of China has totaled more than 300 billion pounds in recent years.

In the United States rice acreage (1966-67) was just under two million - mainly
in California, Arkansas, Louisiana and Texas. Production for the two years
averaged 8 billion, 730 million pounds of rough rice, or approximately 4400
pounds per acre.

Rice has been cultivated since antiquity. Seeding of rice was a religious rite
in China nearly 5000 years ago. The cultivated plant probably originated in
Southeast Asia where wild types still persist. Rice cultivation in Europe began
around 700 A,D. Rice was brought to America by the earliest colonists. All rice
grown in the United States and most of that cultivated in other countries is of
the species Oryza sativa L. This is really a cultivar species, not found
in the wild. Some 20 to 25 species of Oryza are known, but the ancestry
of the cultivated types is uncertain. The species O. glaberrinia Steud.
is cultivated in Africa.

More than 8000 variety names for rice are knonvn, but many of these may be
local names given to similar or identical varieties. However, many hundreds of
varieties distinct in characteristics or in adaptation are known. These are
roughly classed in three groups as follows:

Japonica Group: In general, varieties in this group have short kernels.
Stems are stiff, short and upright. Leaves are short, dark green and the second
leaf forms a narrow angle with the stem. Plants are pubescent and form many
tillers. Panicles are numerous, short, dense and heavy. Spikelets are awnless.
This group is generally grown in more northern climates as Japan, Korea,
Northern China, Europe, and California in this country.

Indica Group: This group is more tropical in adaptation than japonica
varieties and includes the kinds grown in Southern Asia, the Philippines, and
the South-Central States in this country. These varieties are characterized by
long kemels, long, light green leaves, tall, somewhat spreading stems, much
less stiff than stems in japonica varieties. Panicles are numerous, long, light
in weight, medium in density. Spikelets are awnless.

Bulu Group: This group is of minor importance compared with japonica
and Indica. Varieties classed here are grown mainly on the islands off
Southeast Asia. They are somewhat intermediate in characteristics. The kemels
are large, stems are tall, stiff and upright. Panicles are few in number, of
medium length and density, but heavy. Awns are numerous.

Rice Culture

The rice plant differs from most grains in that it thrives best when
grown with the soil surface covered with water. Some rice is grown on soils
that are not flooded; but soils well supplied with moisture are necessary and
even then yields are much less than with flooded rice. This so-called "upland"
rice is not grown in this country.

Rice seed requires a high soil moisture content to germinate. It germinates
and grows readily when seeded on the soil surface under water. Much of the
seeding in this country is on flooded sites, the seed being spread from
airplanes. It may also be drilled in prepared soil, followed by flooding after
growth starts. In Oriental countries where land is scarce, rice is often
started in nurseries and transplanted to the field. This is economical of land
use but does not result in higher yields than seeding in place.

For highest yields, fields are kept flooded from time of seeding or
transplanting until shortly before harvest - with water 4 to 8 inches deep.
Water should not become stagnant. If possible, a slow inflow and outtow of
water should be maintained. An altemative practice is to draw off the old water
and flood with fresh water at intervals.

In the United States nearly all rice is harvested with combines. Water is
withdrawn 2 to 3 weeks before harvest so as to dry the soil enough for combine
operation. Rice so harvested generally contains too much moisture to keep in
storage and must be dried artificially prior to storage. An alternative method,
no longer used in this country, is to mow the rice and let it lie in swaths to
dry prior to threshing. Some modification of this method is widely used in most
countries where rice is grown. In very humid climates the mowed rice may need
to be removed from the field and kept off the ground to permit drying prior to
threshing.

The Rice Plant: Rice is cultivated as an annual although plants will
persist for more than one season, through rooting of tillers, in areas where
freezing does not occur. Whether under water or in moist soil the central stem
first emerges. Within a few days tiller or branch plants grow from buds in leaf
axils near the soil level. The number of such tillers varies with the density
of the plant stand and with the variety. Usually not more than half a dozen
stems develop from a single seed , but up to 50 tillers may form on some kinds
if very widely spaced. Only tilters that form early produce panicles and ripen
grain.

Stem height ranges from less than 20 inches to 6 feet or more. Stems are
hollow between nodes. Tall growing kinds are subject to lodging or falling over
- particularly if fertilized. The shorter- and stiffer-stemmed varieties are
therefore more satisfactory as use of fertilizers generally restilts in greatly
increased yields. Recent development of short, stiff-stemmed varieties adapted
to the tropics - coupled with the increased use of fertilizer possible on such
varieties - is resulting in greatly increased production in South Asian
Countries.

The panicle or seed bearing head roughly resembles that of oats but is more
compact and tends to droop more. The panicle is usually 4 to 10 inches long
with branches that rise singly or in whorls. Each branch bears several
spikelets - each with a single flower. The panicles usually contain from 75 to
150 spikelets, but the number may be greater. The panicle is initially enclosed
in a sheath. It emerces from the sheath about 75 to 80 days after seeding in
the earliest varieties and in 125 to 130 days in late varieties. The period
from panicle emergence to full seed ripeness is about 35 days.

The flower in rice consists of two small, sterile lemmas which partially cover
the developing seed; floral bracts - the lemma and palea; and within these the
stamens and pistil - or sex organs. As in most oat and barley varieties, the
lemma and palea adhere to the developing seed or kernel. The lemma may be awned
but is awnless - or near awnless in most cultivated varieties. The adhering
lemma and palea constitute the "bull" of the threshed grain or so-called
"rough" rice. After the hun is removed in milling the rice is tenned "brown" or
"hulled." The hull comprises about 20 percent of the kernel weight. Further
inilling removes the bran - or seed coat, the germ, and some of the endosperm.
This results in about an additional 10 percent removal by weight.

Milling and Uses of Rice

The primary use of rice is for human food. For such use the hall,
present on the threshed or "rough" rice, is first removed. In Oriental
countries, for home use this may be done by use of a hollow block and wooden
pounder - which leaves the bran layer and the germ on the rice. In the United
States, other Occidental countries, and to a considerable extent in the Orient,
rice is machine milled. This removes the hull, bran, germ, and some of the
endosperm. The first step after cleaning the rice to remove any chaff and
foreign matter, is to pass the kernels through a sheller which may consist of
paired rubber rollers revolving at different speeds. Hulling stones may also be
used. One horizontal stone is stationary and a second one revolves. When
properly spaced they loosen the hulls with minimum kernel breakage. The product
from this step is brown rice, the bran layer and germ being still present on
the grain.

Brown rice is generally further milled in this and other Occidental countries
to remove the bran and germ. This is accomplished by rubbing or scouring. A
final step is termed brushing. It consists of passing the rice through a
rapidly revolving vertical cylinder covered with overlapping pieces of cowhide
or pigskin. This results in a polished surface on the grains.

A step termed parboiling, preliminary to hulling, is often used in Oriental
countries and to some extent in this country. The rough rice is first soaked,
then steamed either under pressure or without pressure, and subsequently dried
before removing the hulls. This results in a toughening of the endosperm and
less breakage. Also, minerals and vitamins present in the bran and embryo move
into the grain proper to some extent, so parboiled rice is higher in these
important nutrients than rice hulled without such treatment. In this country a
process having a similar effect is sometimes used. The rough rice is first put
under vacuum to remove air, then is soaked under pressure and finally steamed
under pressure. This process shortens the time of treatment compared with
parboiling and results in similar reduced breakage of the endosperm and
enhanced nutritive value.

Milled rice is used mainly for direct consumption, usually after cooking by
boiling. It may be sold as precooked or partially precooked rice. Rice is also
used extensively as breakfast foods - as puffed rice, flakes, or rice crispies.
Broken rice may be used as food or in manufacture of alcoholic beverages. Rice
flour, a product of final milling, is used in various mixes. The bran is used
mainly as livestock feed. Rice hulls are used for fuel, insulation, and in
certain manufacturing processes.